Along-shelf Transport and Cross-shelf Exchange Driven by Surface Waves on the Inner Continental Shelf

内陆架表面波驱动的沿陆架运输和跨陆架交换

• 批准号: 1626466
• 负责人: Thomas Connolly
• 金额: $ 12.56万
• 依托单位: San Jose State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1626466&HistoricalAwards=false
• 关键词: Along; shelf; Transport; Cross; Exchange

Exchange across the inner shelf influences the distribution of nutrients, harmful algal blooms, pollutants, larvae and sediment. It is not yet fully understood how surface waves influence this exchange. Recent advances have been made in the numerical modeling of wave-current interactions, but so far these modeling studies have focused on the surf zone. This study will extend these modeling capabilities to the inner shelf by testing model results in the context of laboratory and field observations. This research will drive further development of wave-current coupling in a modeling system that is freely available to the scientific community. The insight into wave-current interaction processes gained during this investigation will improve the development of realistic models used in practical sediment transport applications. Most studies of inner-shelf circulation have focused on the role of wind stress. Surface waves have only recently been recognized as an important forcing mechanism over the inner shelf. Present understanding of the wave-driven inner-shelf circulation is based on analytical models with restrictive assumptions, such as constant turbulent mixing throughout the water column, and no spatial variations across the shelf. The model experiments in this study will allow for more realistic representations of turbulent mixing, and will include the effects of stratification, a sloping bottom and advection of momentum from the surf zone, where breaking waves generate strong along-shelf currents. Few previous studies have quantified the importance of momentum advection on the inner shelf, but it is potentially important near the boundary of the surf zone and will also be assessed in observations. Based on the model experiments, the relative importance of the hypothesized mechanisms under different environmental conditions will be scaled so that results can be applied generally at many locations. The goal of this study is to identify the key processes that determine the observed spatial structure of the circulation driven by surface waves on the inner shelf, which is located offshore of the breaking surf. Previous observations have identified a surface-intensified offshore flow associated with surface waves over the inner shelf. In the direction parallel to shore, new observational analysis shows a complex response to wave forcing that varies with water depth. Two alternative hypotheses are formulated to account for these observations: one in which the Earth's rotation is necessary, and another that involves strong turbulent mixing and transport of momentum from the surf zone. Numerical modeling experiments, with complex physics but idealized geometry, will be carried out to determine the relative contribution of these two mechanisms to the observed wave-driven circulation during different forcing and environmental conditions. A new parameterization for the critical process of "wave streaming" near the bottom will be tested against field and laboratory observations. Model experiments, in combination with new analysis of existing observations, will identify processes that generate exchange between the surf zone and inner shelf during combined wind and wave forcing.

内大陆架的交换影响营养物、有害藻华、污染物、幼虫和沉积物的分布。目前还不完全清楚表面波如何影响这种交换。波流相互作用的数值模拟取得了很大的进展，但迄今为止，这些模拟研究主要集中在碎波带。本研究将通过在实验室和实地观察的背景下测试模型结果，将这些建模能力扩展到内大陆架。这项研究将推动波流耦合的建模系统，是免费提供给科学界的进一步发展。在本次调查中获得的波流相互作用过程的洞察力将提高实际泥沙输运应用中使用的现实模型的发展。大多数对陆架内环流的研究都集中在风应力的作用上。表面波只是最近才被认为是一个重要的强迫机制在大陆架的内部。目前对波浪驱动的内陆架环流的理解是基于具有限制性假设的分析模型，例如整个水柱的恒定湍流混合，以及整个陆架的空间变化。在这项研究中的模型实验将允许更现实的湍流混合表示，并将包括分层的影响，倾斜的底部和平流的动量从碎波区，破碎波产生强大的沿岸流。很少有以前的研究量化的重要性，动量平流的内架，但它是潜在的重要的冲浪区的边界附近，也将在观测中进行评估。基于模型实验，不同环境条件下的假设机制的相对重要性将被缩放，以便结果可以普遍应用于许多位置。本研究的目标是确定的关键过程，确定所观察到的空间结构的环流驱动的内架，这是位于离岸的破碎冲浪的表面波。以前的观测已经确定了一个表面强化的离岸流与表面波的内部大陆架。在平行于海岸的方向上，新的观测分析显示了对波浪作用力的复杂响应，该响应随水深而变化。两种替代假设制定这些意见：一个是地球的旋转是必要的，另一个涉及强湍流混合和运输的动量从冲浪区。数值模拟实验，复杂的物理，但理想化的几何形状，将进行，以确定这两种机制的相对贡献，观察到的波驱动环流在不同的强迫和环境条件。一个新的参数化的关键过程的“波流”附近的底部将测试对现场和实验室观测。模型实验，结合新的分析，现有的观测，将确定过程中产生的冲浪区和内架之间的交流，在风和波浪强迫。